Idling revolution control device for internal combustion engine

Abstract

An idle revolution of an internal combustion engine is controlled by a device which includes an average position deflection operating portion for averaging a position deflection between a predetermined position of an actuator for controlling a throttle valve of the engine and an actual position thereof over a predetermined time period to correct the predetermined position with an average value to thereby obtain a desired idle revolution of the engine. By introducing a short time position deflection into the average position deflection, which corresponds to a temporary variation of engine load, an undesired effect of such variation can be removed.

What is claimed is: 
     
       1. An idle revolution control device for an internal combustion engine associated with a revolution detector for detecting engine revolution, an idle detector for detecting an engine condition in which a throttle valve is not opened, an actuator for controlling an amount of intake air during an idling condition of the engine, and an actuator position detector for detecting a drive position of said actuator and adapted to control said actuator according to information from at least said revolution detector, said idle detector and said actuator position detector, said idle revolution control device comprising: a revolution number feedback control portion for comparing a predetermined revolution number with an actual revolution number from said revolution number detector and for controlling said actuator to control an amount of intake air of said engine in an idling condition so that said actual revolution number converges to said predetermined revolution number;   an average position deflection operating portion for averaging a position deflection between a first predetermined position of said actuator and an actual position thereof when said actual revolution number becomes equal to said predetermined revolution number over a predetermined time period;   a position feedback control portion for adding an averaged position deflection obtained by said average position deflection operating portion to said first predetermined position of said actuator to obtain a second position of said actuator to which the actual position of said actuator is controlled;   a selection circuit for selecting an output of said revolution number feedback control portion when said throttle is in the idle condition and an output of said position feedback control portion when said engine is out of idle condition or a vehicle mounting said engine is moving; and   a drive portion for driving said actuator according to an output of said selection circuit to force said actuator to said second position.   
     
     
       2. The idle revolution control device as claimed in claim 1, wherein said time period for averaging said position deflection is from about 30 seconds to about 30 minutes. 
     
     
       3. The idle revolution control device as claimed in claims 1 or 2, wherein said average position deflection obtained by said average position deflection operating portion is kept stored in a memory element even when an ignition key of said engine is in an off state. 
     
     
       4. The idle revolution control device as claimed of claims 1 or 2 wherein said average position deflection operating portion operates to provide an initial average position deflection value corresponding to a position in which intake air is increased by an amount corresponding to an idle load variation experienced when a battery of the vehicle is initially connected thereto. 
     
     
       5. The idle revolution control device as claimed in claim 1, wherein said average position deflection operating portion further operates to calculate a short time position deflection and said second position of said actuator is set as a sum of average position deflection and said short time position deflection. 
     
     
       6. The idle revolution control device as claimed in claim 5, wherein said summation of said short time position deflection to said average position deflection is stopped when the vehicle is moving. 
     
     
       7. The idle revolution control device as claimed in claim 5, wherein said summation of said short time position deflection to said average position deflection is stopped when engine revolution is not less than 1000 rpm. 
     
     
       8. The idle revolution control device as claimed in any of claims 5 to 7, wherein said revolution feedback control is prohibited when a result of said summation is not less than a predetermined value.